PROFINET Design Guideline Summary

PROFINET
Design Guideline

Order No.: 8.062

PROFINET Design Guideline
11/2010

© Copyright by:
PROFIBUS Nutzerorganisation e.V.
Haid-und-Neu-Str. 7
76131 Karlsruhe Version 1.04
Germany
Phone: +49 721 96 58 590 November 2010
Fax: +49 721 96 58 589
e-mail: info@profibus.com
http: //www.profibus.com

PROFINET

Design Guideline

Version 1.04

November 2010

Order No: 8.062

Page 1 / 190
© Copyright by PNO 2010 – all rights reserved

Introduction

PROFINET Order No: 8.062

Identification: TC2-10-0002

This document has been created by the “Installation Guide”

(TC2 WG13) workgroup of the PROFIBUS User Organization.

Published by:

PROFIBUS Nutzerorganisation e.V. (PROFIBUS User Organization)

Haid-und-Neu-Str. 7

76131 Karlsruhe

Germany

Phone: +49 721 / 96 58 590

Fax: +49 721 / 96 58 589

info@profibus.com

www.profinet.com

All rights reserved, including reprint, reproduction (photocopy, microfilm), storage in
data processing systems and translation, both in extracts and completely.

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Introduction

Revision log

Version Date Changes/history

1.04 18.11.2010 Final version

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Introduction

Table of contents

1 Introduction ...............................................................13
1.1 Preface .......................................................................................... 14

1.2 Liability exclusion........................................................................ 15

1.3 PNO documents ........................................................................... 16

1.4 Referenced standards ................................................................. 17

1.5 Symbols and their meaning........................................................ 19

1.5.1 Symbols for structuring the text ........................................................... 19

1.5.2 Symbols for components ...................................................................... 20

1.5.3 Symbols for areas .................................................................................. 21

1.5.4 Symbols for PROFINET cables.............................................................. 22

1.6 Template for documentation of design process ...................... 23

1.7 About the structure of this guideline......................................... 24

1.8 Goal of the guideline ................................................................... 26

2 Analysis and preliminary considerations ...............27
2.1 Determination of automation components ............................... 29

2.2 Device selection........................................................................... 33

2.2.1 The PROFINET Conformance Classes ................................................. 34

2.2.2 Special timing requirements ................................................................. 36

2.2.3 Further criteria for device selection...................................................... 40

2.3 Definition of device types ........................................................... 46

2.4 Documentation of results ........................................................... 48

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Introduction

3 Network topology ......................................................49
3.1 PROFINET Topology ................................................................... 51

3.2 Applicable transmission media.................................................. 55

3.2.1 PROFINET copper cabling..................................................................... 56

3.2.2 PROFINET optical fiber cabling............................................................. 62

3.2.3 Selection of required connectors.......................................................... 68

3.3 Definition of network topology................................................... 71

3.4 Topology check and refinements .............................................. 76

3.5 Documentation of topology ........................................................ 77

4 Special design aspects.............................................79
4.1 Integration of standard Ethernet devices.................................. 80

4.2 Use of “Fast Start-up“ ................................................................. 83

4.3 Use of existing cable infrastructure .......................................... 84

4.4 Connection to higher level networks (enterprise network)..... 85

4.5 Consideration of high network loads ........................................ 87

4.6 Documentation of modified network topology ......................... 89

5 Performance considerations ....................................91
5.1 PROFINET network load ............................................................. 93

5.2 Ethernet network load ................................................................. 99

5.3 Overall consideration ................................................................ 100

5.4 Performance optimization......................................................... 102

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Introduction

6 Planning of additional functions............................105
6.1 Increased availability................................................................. 107

6.2 Wireless transmission technology .......................................... 113

6.3 Access for engineering tools ................................................... 116

7 Definition of device parameters .............................117
7.1 Assignment of names ............................................................... 119

7.2 Planning of IP addresses .......................................................... 121

7.3 PROFINET plant example.......................................................... 124

8 Summary..................................................................129

9 Annex .......................................................................131
9.1 Addresses................................................................................... 132

9.2 Glossary...................................................................................... 132

9.3 Details about PROFINET copper cables.................................. 133

9.4 Details about PROFINET optical fibers ................................... 143

9.5 Selection of connectors ............................................................ 148

9.6 Cabling examples ...................................................................... 162

9.7 Selection of switches ................................................................ 168

9.8 Power supply ............................................................................. 172

9.9 Network load calculation tool................................................... 179

10 Index.........................................................................185

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Introduction

List of figures

Figure 1-1: Design structure ................................................................................ 24

Figure 2-1: Floor plan of a plant with pre-placed components......................... 30

Figure 2-2: Sample layout plan of a plant with special assignment................. 31

Figure 2-3: Classification and content of the individual
conformance classes ....................................................................... 35

Figure 2-4: Coverage of requests by communication and application ............ 38

Figure 2-5: Coverage of communication timing requirements ......................... 39

Figure 2-6: Use of PROFIsafe via PROFINET ..................................................... 43

Figure 2-7: Difference integrated switch and separate switch ......................... 44

Figure 2-8: Sample layout of a plant with device preselection ......................... 46

Figure 3-1: Star topology ..................................................................................... 52

Figure 3-2: Tree topology..................................................................................... 53

Figure 3-3: Line topologies with internal switches............................................ 54

Figure 3-4: Application of optical fiber technology for EMI .............................. 62

Figure 3-5: Example of a factory automation ..................................................... 73

Figure 3-6: Example of a machine automation................................................... 74

Figure 3-7: Example plant process automation ................................................. 75

Figure 3-8: Plant example with preliminary topology........................................ 78

Figure 4-1: Plant example with integration of standard Ethernet devices....... 81

Figure 4-2: Implementation of “Fast Start-up“ with PROFINET........................ 83

Figure 4-3: Plant example with connection to the corporate network ............. 85

Figure 4-4: Detail of plant example before the adjustment ............................... 87

Figure 4-5: Detail of plant example after the adjustment .................................. 88

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Introduction

Figure 5-1: Structure of PROFINET transmission cycle .................................... 93

Figure 5-2: Weaknesses caused by high network load..................................... 95

Figure 5-3: Impact of the switch on processing times ...................................... 97

Figure 5-4: Adjustment of line depth .................................................................. 98

Figure 5-5: Overall performance consideration ............................................... 100

Figure 5-6: Adjustment of plant topology and/or of the
transmission clock ......................................................................... 103

Figure 6-1: Device exchange in a line topology ............................................... 107

Figure 6-2: Device exchange in a star or tree structure .................................. 108

Figure 6-3: Upgrading a line topology to a ring structure............................... 108

Figure 6-4: High-availability plant network....................................................... 111

Figure 6-5: Use of wireless transmission technology ..................................... 113

Figure 6-6: Diagnosis and engineering access................................................ 116

Figure 7-1: PROFINET IO Device (delivery status)........................................... 119

Figure 7-2: PROFINET IO Device (address allocation) .................................... 121

Figure 7-3: Overall structure of example plant................................................. 124

Figure 9-1: PROFINET cable type A .................................................................. 137

Figure 9-2: PROFINET PE cable ........................................................................ 138

Figure 9-3: PROFINET ground cable................................................................. 139

Figure 9-4: Trailing cable ................................................................................... 140

Figure 9-5: cables for festoons.......................................................................... 141

Figure 9-6: PROFINET optical fiber cable ......................................................... 146

Figure 9-7: PROFINET FO trailing cable ........................................................... 147

Figure 9-8: RJ45 push-pull in IP 65 version...................................................... 151

Figure 9-9: RJ45 in IP 20 version....................................................................... 151

Figure 9-10: M12 connector ............................................................................... 152

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Introduction

Figure 9-11: SCRJ connector in IP 20 ............................................................... 154

Figure 9-12: SCRJ Push-Pull connector ........................................................... 155

Figure 9-13: M12 hybrid connector ................................................................... 156

Figure 9-14: RJ45 distribution module for top hat rail
mounting in IP 20 environments.................................................. 158

Figure 9-15: RJ45 socket for IP 65 / IP 67 environments................................. 159

Figure 9-16: RJ45 Push-Pull wall duct for installation
with switch cabinets ..................................................................... 160

Figure 9-17: M12 wall duct for installation with switch cabinets.................... 161

Figure 9-18: Example of copper-based cabling ............................................... 162

Figure 9-19: Example of FO cabling.................................................................. 164

Figure 9-20: Representation of attenuation balance for single-
mode optical fiber links................................................................. 166

Figure 9-21: Representation of attenuation balance for POF FO link ............ 167

Figure 9-22: Flow chart: Selection of grounding method................................ 175

Figure 9-23: Multiple grounding of system grounds ....................................... 177

Figure 9-24: Measuring facility for monitoring of system
ground zero potential ................................................................... 177

Figure 9-25: User interface of the network load calculation tool.................... 179

Figure 9-26: Network load calculation using average values ......................... 181

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Introduction

List of tables

Table 1-1: Symbols for structuring the text........................................................ 19

Table 1-2: Symbols for components ................................................................... 20

Table 1-3: Symbols for areas ............................................................................... 21

Table 1-4: Symbols for PROFINET cables .......................................................... 22

Table 2-1: PROFINET data channels ................................................................... 36

Table 2-2: Differentiation between application and communication................ 38

Table 2-3: Connection technologies for PROFINET devices ............................ 42

Table 2-4: Benefits of both switch connection options..................................... 45

Table 3-1: Specific attenuation of fiber types..................................................... 63

Table 3-2: Attainable transmission links of optical fiber types ........................ 64

Table 3-3: Maximum permissible PROFINET end-to-end link attenuation....... 65

Table 3-4: Attenuation of splices and connector pairs...................................... 66

Table 3-5: Use of different fiber types................................................................. 66

Table 3-6: Transmission link length and connector pairs (copper) ................. 69

Table 3-7: Transmission link length and connector pairs (FO) ........................ 70

Table 5-1: PROFINET network load in percent................................................... 96

Table 5-2: Comparison of “Store and Forward” and “Cut Through” ............... 97

Table 5-3: Approaches for performance optimization..................................... 102

Table 7-1: Private IPv4 address ranges ............................................................ 122

Table 7-2: Overview of number of PROFINET network nodes ........................ 125

Table 7-3: Address selection in automation plant 1 ........................................ 128

Table 9-1: Cable parameters PROFINET Type A copper cable ....................... 133

Table 9-2: Cable parameters PROFINET Type B copper cable ....................... 134

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Introduction

Table 9-3: Cable parameters PROFINET Type C copper cable ....................... 134

Table 9-4: Mechanical properties of PROFINET copper cables...................... 135

Table 9-5: Mechanical properties of single / multimode FO............................ 143

Table 9-6: Mechanical properties of POF optical fibers .................................. 144

Table 9-7: Mechanical properties of PCF optical fibers .................................. 144

Table 9-8: Types of FO cables ........................................................................... 146

Table 9-9: Material list copper-based cabling .................................................. 163

Table 9-10: Material list FO cabling................................................................... 165

Table 9-11: Calculation of end-to-end link attenuation for
single-mode fibers .......................................................................... 166

Table 9-12: Calculation of end-to-end link attenuation for
polymer fiber links .......................................................................... 167

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Introduction

- Intentionally left blank -

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Introduction

1 Introduction

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Introduction

1.1 Preface
The goal of this PROFINET Design Guideline is to support engineers who have to
design PROFINET automation systems, to facilitate the professional design of
plants and to serve as a helpful guide for the step-by-step design of a plant.

The information is presented in a way which tries to be as brief and easy to under-
stand as possible. It is nevertheless assumed that users have basic knowledge of
PROFINET technology, electrical engineering and network technology.

This guideline is not intended as a PROFINET compendium. If you need more de-
tailed information about PROFINET, please use the appropriate documents pub-
lished by PROFIBUS Nutzerorganisation e.V. or comparable technical literature.
This guideline does not cover the installation and commissioning of PROFINET.
Please refer to the PROFINET Installation Guideline (Order No: 8.071) and the
PROFINET Commissioning Guideline (Order No. 8.081) for more details.

This Design Guideline does not replace any previous documents. It is intended as
an application-oriented complement to the other guidelines. The previous PNO
documents therefore continue to be valid.

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Introduction

1.2 Liability exclusion
The PROFIBUS User Organization has taken utmost care in the preparation of this
document and compiled all information to the best of their knowledge. This docu-
ment is nevertheless based on present knowledge, is of an informative character
and is provided on the basis of a liability exclusion. Therefore, this document may
be subject to change, enhancement or correction in the future without any refer-
ence. PROFIBUS Nutzerorganisation e.V. expressively refuses all types of contrac-
tual or legal liability for this document, including the warranty for defects and the
assurance of certain usage properties. Under no circumstances shall PROFIBUS
Nutzerorganisation e.V. accept liability for any loss or damage caused by or result-
ing from any defect, error or omission in this document.

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Introduction

1.3 PNO documents

Download of PNO documents at:

www.profinet.com

PROFINET Installation Guideline

Order No.: 8.071 Version 1.0, January 2009

PROFINET Commissioning Guideline

Order No.: 8.081 Version 1.0, June 2010

PROFINET Security Guideline

Order No.: 7.002, Version 1.0, March 2005

PROFINET Architecture Description and Specification

Order No.: 2.202, Version 2.0, January 2003

PROFINET System Description

Order No.: 4.131, Version April 2009

PROFIBUS and PROFINET Glossary


Conformance Class A Cabling Guideline

Order No.: 7.072, Version 1.0, July 2008

PROFINET Cabling and Interconnection Technology

Order No.: 2.252, Version 2.0, March 2007

Physical Layer Medium Dependent Sublayer on 650 nm Fiber Optics

Technical Specification for PROFINET


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Introduction

1.4 Referenced standards
IEC 11801 (2002)

Information technology – Generic cabling for customer premises

IEC 24702 (2006)

Information technology - Generic cabling - Industrial premises

IEC 60364-4-41(2005)

Electrical installations of buildings - Part 4-41: Protection for safety - Protection
against electric shock

IEC 60364-5-54 (2002) / VDE 0100-540

Selection and erection of electrical equipment - Earthing arrangements, protective
conductors and protective bonding conductors

IEC 60529 (2001)

Degrees of protection provided by enclosures (IP Code)

EN 50174-3 (2003)

Installation technology – Cabling installation - Part 3: Installation planning and prac-
tices outside buildings

IEC 61140 (2001)

Protection against electric shock - Common aspects for installation and equipment

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Introduction

IEC 61300-3-4 (2001)

Fiber optic interconnecting devices and passive components - Basic test and
measurement procedures - Part 3-4: Examinations and measurements - Attenua-
tion

IEC 61158-2 (2007)

Industrial communication networks – Fieldbus specification – Part 2: Physical layer
specification and service definition

IEC 61918 (2010)

Industrial communication networks – Installation of communication networks in
industrial premises.

IEC 61784-5-3 (2010)

Industrial communication networks – Profiles – Part 5-3: Installation of fieldbuses –
Installation profiles for CPF 3

EN 50310 (2006)

Application of equipotential bonding in buildings with information technology equip-
ment

EN 50174-2 (2009)

Information technology – Cabling installation – Part 2: Installation planning and
practices inside buildings

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Introduction

1.5 Symbols and their meaning
The figures used in this guideline will help you better understand the text. In addi-
tion, symbols for text structuring will be used. These symbols highlight important
text passages or summarize certain sections.

1.5.1 Symbols for structuring the text

Symbol Name Meaning

Used to mark a recommendation and / or
Tip
summary of the current topic.

Used for information which, if not ob-
served,
Important
may result in malfunctions of

plant operation.

Instruction
Used for direct instructions

Used to mark

danger to life and health.
Danger!
The observance of an instruction marked
in this way is extremely important!

Table 1-1: Symbols for structuring the text

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Introduction

1.5.2 Symbols for components

Symbol Name Meaning

Operator
console Human System Interface (HSI).

An engineering station or PC with commis-
IO Supervisor sioning and diagnostic functions for
PROFINET IO

A device (typically a control unit) that initi-
IO Controller
ates the IO data traffic.

Network component for interconnecting
Router
data traffic between different sub-networks.

Network component for the interconnection
Switch
of several PROFINET devices.

Remotely assigned field device which is
IO Device
assigned to an IO controller.

IO device with Remote field device with wireless connec-
wireless
tivity
connection
Device which provides a transition from
Wireless wired transmission to wireless transmis-
access point
sion.

Converter from one physical medium to
Media
converter another.

Video camera Device for image-based monitoring

Control station Standard PC with control functions

Table 1-2: Symbols for components

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Introduction

1.5.3 Symbols for areas

Symbol Name Meaning

Area where the occurrence of electro-
EMI EMI magnetic interference (EMI) must be
expected.

Table 1-3: Symbols for areas

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Introduction

1.5.4 Symbols for PROFINET cables

Symbol Name Meaning

Standard Ethernet connection which
Standard Ethernet does not involve the PROFINET
protocol

PROFINET Industrial Ethernet ca-
ble with copper wires

PROFINET copper ca- sheath color: green
ble
The dotted line indicates a connec-
tion with increased determinism
requirements.

Fiber-optic cable

sheath color: green

Note: for easier differentiation be-
tween copper and FO, the FO are
FO highlighted orange in this guideline
although the cable sheath is usually
green.
Once again, the dotted line indi-
cates a connection with increased
determinism requirements.

Conductive link Electrically conductive link

Table 1-4: Symbols for PROFINET cables

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Introduction

1.6 Template for documentation of design process
In general, the design process should be documented throughout the entire proc-
ess. For this purpose you can use internal documentation tools based on your in-
ternal standards.

In addition, a large number of planning tools offer additional functions for the docu-
mentation of automation plant design.

Automation plant documentation supports the correct installa-
tion and commissioning. During the design process you
should document all modifications in order to ensure correct
operation in the future.

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Introduction

1.7 About the structure of this guideline
The structure of this guideline corresponds to the design process. This process will
be followed step by step, while each modification in a later process shows a possi-
ble implication on the previous steps. Figure 1-1 shows the structure of the design
process.

Analysis and
Preview

Rough planning

Detailed planning

Consideration of
additional functions

Figure 1-1: Design structure

The chapters of this design document follow this procedure. While chapter 1 con-
tains an introduction, the following chapters go from general issues to the details of
the design process. The chapters highlight the following issues:

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Introduction

• Chapter 2: This chapter starts with a preview and analysis of the process
to be automated. The properties and the placement of the automation
components are described.

• Chapter 3: This chapter includes the topology definition of the automation
plant based on the findings gathered in chapter 2.

• Chapter 4: The existing basic design is extended by such cases which are
typically not part of PROFINET.

• Chapter 5: In order to ensure the performance in a PROFINET network,
based on the previous chapters, the network load and the update rates are
considered.

• Chapter 6: PROFINET offers a multitude of possible applications for addi-
tional functions which require a special consideration. The chapter pro-
vides an overview of these functions.

• Chapter 7: This chapter describes a careful planning of name and address
assignment

• Chapter 8: This provides a short summary of design results.

The annex (chapter 9) of this document also provides additional information about
different components and their properties which are used in a PROFINET network.
This includes information such as cable parameters or application examples for
cable design and many more.

An index is provided in chapter 10 to facilitate the search for topic-related informa-
tion in the guideline.

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Introduction

1.8 Goal of the guideline
The main goal of this guideline is to help you to select devices and networking
components for a PROFINET system and to design and layout the system to give
reliable performance and allow easy installation, commissioning and maintenance,

After completion of the design process, the following information should be avail-
able or be generated.

• Plant design

• Topology

• Selection of components

• Selection of transmission medium

• Selection of connectors

• Communication relations

• Estimate of data volumes to be transmitted

In case any of this information should be missing, the design
process has to be restarted at the relevant position.

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Analysis and preliminary considerations

2 Analysis and preliminary considerations

Page 27 / 190


Before planning can start …

…you need an overview of your project. For example this may include the physical
layout, a plan of the plant or the plant schematics.

This information provides a first idea of the extent of the PROFINET network to be
designed.

The goal of the next section is to analyze and to describe the process to be auto-
mated.

The properties and the placement of the individual automation components will be
defined. In addition, information will be provided about the points to be considered
when selecting the components.

In general you should always bear in mind that the design
process and the individual steps included are part of an itera-
tive process which may have to be carried out several times.

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2.1 Determination of automation components
In the following step, the designer has to determine the components for plant auto-
mation. First, each component needs to be appropriately placed based on the plant
design information or the building floor plan..

For example:

• Controller placement in a separate switch cabinet away from the process
or together with other PROFINET devices close to the process,

• Remote I/O placed close to the process or in a remote cabinet,

• Display panels for control close to the process or geographically remote for
monitoring,

• etc.

The required components should then be added to the layout plan of the automa-
tion plant. Then the components should be grouped in such a way that

• a geographical and

• functional assignment of the components

is achieved.

The geographical assignment is usually created by considering the geographical
proximity in the layout plan. The functional assignment is determined via common
control tasks which can be determined from the mutual data exchange between
control and periphery. It also makes sense to create a functional grouping according
to the conformance classes (see next chapter).

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Process automation plant

Figure 2-1: Floor plan of a plant with pre-placed components

In Figure 2-1, the initial placement of the automation components has been com-
pleted with the PROFINET devices positioned according to the task in the automa-
tion plant.

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Automation island A

Automation island B

Figure 2-2: Sample layout plan of a plant with special assignment

Figure 2-2 shows the geographical and functional assignment of components. The
automation plant is sub-divided into two islands. This is the result of local conditions
which may occur, in this case, different plant areas.

The relation of the controllers in automation island B requires not only a geographi-
cal differentiation, but also a functional differentiation - a fact that is indicated by the

Page 31 / 190


additional gray frames in automation island B. Another example might be a common
task within the plant part but where each individual part has to meet different re-
quirements.

There is also an additional geographical separation within the second plant part in
automation island B since the PROFINET IO devices must be positioned separately
from the rest.

It is furthermore necessary to identify any communication relations that are required
between the control systems. These relations are shown as arrows in the example.
At a later stage of design you have to check whether the required communication
relation can be realized for the selected devices. If this is not the case, you have to
foresee additional hardware components.

Direct communication between the control systems is required within island B, it is
also necessary for these controllers to communicate with the control system within
island A.

At this point, the components are not interconnected, but only
positioned in the automation plant and combined to groups
with different functionalities.

Mark the areas with increased requirements, e.g. determin-
ism, to ensure they can be considered separately during the
design.

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2.2 Device selection
Depending on the required positions of the automation components within the plant,
the PROFINET devices can now be selected. This chapter describes the preselec-
tion of PROFINET network nodes and their properties.

In general, the following criteria should be observed:

• Conformance Class

• Time requirements

• Consideration of device function

• Feasibility of the required communication relations

• Type of connection of PROFINET device (copper cable or FO with appro-
priate connection technology)

• Protection class of device

• other specifications

The preselection of devices according to the following criteria
makes sure that your components are able to fulfill the auto-
mation task. You should also check the manufacturer data of
the selected devices for possible restrictions and require-
ments.

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2.2.1 The PROFINET Conformance Classes
The functionality of the PROFINET components has been categorized into applica-
tion classes or so-called Conformance Classes (CC). The target of these categories
is to define reasonable functionalities in order to narrow down the decision criteria
for plant operators when using PROFINET components.

For detailed information on the individual conformance classes,
please use the document “PROFINET Conformance Classes“
(Order No: 7.041) provided by the PROFIBUS User Organisation.

After assigning an application to a CC, the user can select a number of components
which definitely meet the defined minimum requirements. All CCs already have a
certain basic functionality. This may e.g. include:

• Cyclic data traffic

• Acyclic data traffic

• Identification and maintenance functions

• Prioritization of data traffic

• Basic mechanism for neighborhood screening and device swapping

Another grading has been added to these basic functions. So each conformance
class (CC-A, CC-B, CC-C) defined different functionalities.

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In general, these classes cover content such as

• the type of communication (TCP/IP and real-time communication),

• the transmission medium (copper, FO, wireless) used,

• synchronized communication and

• the redundancy behavior.

Figure 2-3 shows the structure of the conformance classes as well as an extract of
their functionality.

• Synchronous communication
• Certification of network components with hardware support

Conformance Class C
• Certified network components
• Use of SNMP

Conformance Class B
• Simple exchange of devices
Conformance Class A

• Certified devices and controllers
• Diagnosis and alarms
• Cyclic and acyclic data exchange
• Standard Ethernet communication
•
- Cable length
Standard Ethernet diagnostic options
- Attenuation
- Sending of test data packets
C t lk

Figure 2-3: Classification and content of the individual conformance classes

As you can see from the figure, CC-B includes the functionality of CC-A. The same
is true for the functionality of CC-C which in turn includes the functionality of CC-B
and thus also CC-A.

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You should define the conformance class of each device in the
design phase. To ensure that the required functionality will be
available in a certain PROFINET device.

Mark the plant parts that are subject to special requirements. You
should check whether the conformance class you have defined
really covers this requirement profile, and adjust the selection of
PROFINET devices accordingly.

2.2.2 Special timing requirements

General information on communication

While a real-time channel is used for cyclic transmission of process data,
PROFINET offers an additional channel based on standard Ethernet communica-
tion (standard channel) for acyclic services such as parameterisation and diagnosis.
Table 2-1 shows the basic differences between these two communication channels.

Standard channel Real-time channel

• Reading of diagnostic data • Cyclic data exchange

• Acyclic data exchange • Synchronous data exchange

• Device parameterisation • Alarms

Table 2-1: PROFINET data channels

PROFINET also enables unrestricted open TCP/IP data traffic (non real-time data
traffic), with real-time communication getting higher priority against non real-time
communication.

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In addition to the terms mentioned above, the following terms have been estab-
lished for PROFINET transmission technologies:

• IRT: Isochronous real-time, for a cyclic and synchronous data transmis-
sion.

• RT: Real-time for a cyclic data transmission.

• NRT: Non real-time for an acyclic data transmission (e.g. TCP / IP,
UDP / IP)

For more detailed information about the structure of commu-
nication and the properties of data channels, please use ap-
propriate literature.

Page 37 / 190


Definition of the timing requirements

Depending on the target group, PROFINET devices face different requirements in
terms of timing. In general we distinguish between the timing of the application on
the automation plant and the communication on PROFINET.

Communication Application

• Synchronous and cyclic com- • Synchronous application
munication • Cyclic application

• Cyclic communication

Table 2-2: Differentiation between application and communication

The communication has to be fit to the application. Figure 2-4 shows the common
coverage of time requests that have to be considered for the selection of
PROFINET devices.

Application

Cyclic Synchronous

Synchronous and cyclic
communication

Cyclic
communication

Communication

Figure 2-4: Coverage of requests by communication and application

It can be seen clearly that a synchronous application can only be realized via a
synchronous communication. To facilitate the selection of PROFINET devices, the
various conformance classes include appropriate communication request profiles,
starting from CC-A with a simple standard Ethernet transmission, up to CC-C for a
synchronous transmission.

Page 38 / 190


Conformance Class C
CC-C integrates the CC-B functions and provides some more Synchronous
such as e.g. high determinism requirements. IRT is part of
CC-C, just as bumpless redundancy.
Conformance Class B
CC-B combines all CC-A functions and provides some
more such as e.g. neighborhood communication using
LLDP or the network management protocol SNMP.

Conformance Class A Cyclic
CC-A offers the opportunity to connect the devices via
standard Ethernet. With PROFINET, real-time commu-
nication has been added to standard Ethernet. The CC-
A also provides opportunities for alarm management
and addressing and much more. Wireless connectivity is
only included in CC-A.

Figure 2-5: Coverage of communication timing requirements

Since every higher level CC includes the functionality of the lower level CC, any
higher level CC provides enhanced communication functionality (e.g. LLDP,
SNMP). To make sure that the PROFINET devices meet these requirements pro-
files, the device manufacturer has to carry out a certification test.

Always use certified PROFINET devices with the appropriate
requirement profile. You can thus make sure that these de-
vices have been configured for the relevant automation task.
You should determine which requirement profile your
PROFINET devices have to meet.

Page 39 / 190


2.2.3 Further criteria for device selection
Further important criteria for the selection of devices will be explained in more detail
on the following pages. This includes points such as:

• End user specifications,

• Environmental requirements,

• Connection to PROFINET device,

• PROFIsafe and

• PROFINET devices with integrated switch.

End user specifications concerning device selection

In many cases, the requirement profile of an automation plant has been predeter-
mined. In such cases it is common practice for the design or the selection of de-
vices to use so-called approval lists which are provided by the end user. These lists
include the components approved by the end user. The goal of such an approval list
is:

• to reduce the selection process time and effort,

• to use homogeneous components in the entire plant and

• to always have the same requirement profile available.

Device selection specifications provided by the end user must always be observed.
It is also important that the approval lists correspond to the specifications of the
conformance classes.

You should check whether the latest version of approval lists
is available to you.

Page 40 / 190


Environmental requirements for the PROFINET device

Environmental aspects must also be considered for the selection of PROFINET
devices when planning an automation plant. With reference to the location of the
devices, we basically differentiate between the installation in a cabinet and the
unprotected installation in the plant environment.

Both environments imply certain requirements for the nodes of the PROFINET
network.

• Penetration of foreign objects and liquids (IP protection class).

• Mechanical requirements, e.g. vibration, shock

• Temperature influences

• Electromagnetic influences

In order to optimize your device selection, mark those areas
of the plant that generate special requirements for the
PROFINET device to be installed.

For the device selection, consider potential external influ-
ences. Adjust your device selection according to the manu-
facturer information.

Page 41 / 190


Type of connection at the PROFINET device

PROFINET supports many different types of connection to the network. Copper
cabling is normally used for the connection of PROFINET devices. Optical fiber and
wireless communication can also be used.

Several connection technologies are available when using wired transmission me-
dia. These connection technologies can be categorized according to their transmis-
sion medium, as shown in Table 2-3.

Copper cable connections Optical fiber connections

• M12 • M12

• RJ45 (IP20) • SCRJ (IP20)

• Push-Pull-RJ45 (IP65) • SCRJ Push-Pull (IP65)

Table 2-3: Connection technologies for PROFINET devices

The connection technology is determined by the selected
PROFINET device. In a later design step, additional media
converters may be necessary due to certain topology or envi-
ronmental requirements (see chapter 3).

All connectors and cables are PROFINET components that
require a manufacturer declaration concerning the compliance
with PROFINET standards.

Take a note of the connection technology of the selected
device since this may require adaptation at a later stage.

Page 42 / 190


PROFIsafe via PROFINET

PROFIsafe is a standard for safety-relevant communication. It ensures that people
and machinery will not suffer any damage during the operation of an automation
plant. Figure 2-6 shows the use of PROFIsafe devices in a PROFINET network.

PROFIsafe via PROFINET
Emergency stop

Figure 2-6: Use of PROFIsafe via PROFINET

The safety-relevant PROFIsafe communication (yellow) is transmitted over the
same network as the standard PROFINET communication. No separate network is
required. All nodes of the safety-relevant communication must be certified accord-
ing to IEC 61010 (the equipment CE label).

For the device selection you should consider safety-relevant
aspects to ensure that damage to people and machinery has
to be averted during operation. PROFIsafe devices must be
both PROFINET and PROFIsafe certified.

You will find more information about PROFIsafe in the
IEC 61784-3-3 as well as under www.PROFIsafe.net.

Page 43 / 190


Use of switches or integrated switches

PROFINET devices are connected to the network via switches. Switches route the
PROFINET data traffic through the network. Many devices offer the functionality of
an integrated switch. Figure 2-7 shows the difference between the connection via
an integrated switch or via a separate switch.

Figure 2-7: Difference integrated switch and separate switch

While a system based on integrated switches does not require any additional com-
ponent for routing, a device without integrated switch may require an additional
separate switch.

Note that when using integrated switches in a line structure, device failure or re-
placement can cause all devices downstream from the failure to also fail. Generally
a star or tree structure using separate switches gives improved availability in the
event of device failure and replacement.

PROFINET devices equipped with an integrated switch can
provide different numbers of ports.

Use the plan to check whether additional switches may
be required.

Page 44 / 190


Table 2-4 lists the benefits of switch connection options.

Benefits of separate switches Benefits of integrated switches

• Replacement of defective network • Cost reduction since no additional
nodes without interruption of the switch is required
remaining communication for star
• Replacement of defective network
and tree topologies
nodes without interruption of the
remaining communication for line
topology with ring redundancy

Table 2-4: Benefits of both switch connection options

Switches as separate devices are required if your PROFINET devices are not
equipped with integrated switches or if it is necessary due to the distribution of net-
work nodes within the plant.

The requirements for system availability during device failure
and replacement will often dictate when you should use inte-
grated or separate switches.

The selection criteria of the PROFINET network nodes with
respect to device properties and environmental requirements
must also be determined for separate switches.

You should define a suitable number of additional sepa-
rate switches for the future definition of the network to-
pology.

As of conformance class B, switches in PROFINET networks
are treated as IO devices. If separate switches are needed a
support for the selection is provided in the Annex of this doc-
ument.

Page 45 / 190


2.3 Definition of device types
Devices can now be selected based on the information available concerning the
plant as well as the environmental conditions and the requirements to the automa-
tion task.


Automation island A

CC-B

Automation island B

CC-C

CC-B

Figure 2-8: Sample layout of a plant with device preselection

Page 46 / 190


Figure 2-8 shows the sample plant with device preselection. It also shows the as-
signment to different conformance classes and their time requests. Further analysis
shows that some devices are equipped with integrated switches.

In this sample the Automation island A is assigned to the requirements of CC-B.
Island B is also subject to these requirements. In this case a plant area is subject to
higher determinism requirements, which requires an additional categorization. This
area is categorized in conformance class C due to these higher requirements.

The device selection may have to be modified at a later stage
in order to adjust the connection technology and the transmis-
sion medium to the requirements.

You should once more check whether all requirements to the
positioning and the properties of the devices have been con-
sidered.

During the design you should take into account the grounding
as well as an equipotential bonding for the network nodes. In
the Annex of this document you will find information about
power supply and grounding of network nodes in PROFINET
systems.

Page 47 / 190


2.4 Documentation of results
After completion of the analysis and preview of the automation task, all information
concerning device selection should be available to you. This includes device infor-
mation such as

• Device connection or transmission medium (copper, POF, HCS, optical fi-
ber (mono-mode, single mode) or wireless),

• Number of integrated switch ports at the PROFINET device and

• the conformance class

In the automation task, mark the PROFINET devices and the
related applications that are subject to high real-time require-
ments. These devices must be considered separately during
the design process.

You should not carry out a detailed planning of device pa-
rameters at this point. These will be covered in later sections.

You should document the selection of PROFINET devices
and collect all relevant information. Generate lists of the se-
lected devices and their properties.

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Network topology

3 Network topology

Page 49 / 190

Network topology

The previous chapter covered the analysis of the automation task and selection of
components to be used in the plant.

The next step is to create the network topology. First some general topology exam-
ples will be described, followed by a short overview of the possible transmission
media and their most important properties.

Later on, specific examples are provided for typical network topologies in automa-
tion plants.

After the topology and required transmission media have been defined, we must
check that the selected devices suite for the connection of the selected transmis-
sion media.

Finally the topology design will be documented.

The information concerning transmission media and connec-
tors considered here is only a short overview of the most
important data.

Please use suitable sources (e.g. the manufacturer) for more
detailed information.

Page 50 / 190

Network topology

3.1 PROFINET Topology
Flexiblity in network design and layout is a key feature of PROFINET. Since all
standard Ethernet topologies are used, PROFINET supports an almost unlimited
number combination options.

The network topology mainly results from criteria such as:

• The location of the components,

• the distances to be covered,

• the EMC requirements,

• electrical isolation requirements,

• conformance class, requirements,

• requirements for increased availability and

• consideration of network loads.

The selection of the correct topology is important for the future
design of the PROFINET automation plant. The topology may
have to be adjusted in a later design step.

Additional external switches may be required to create the
topology. You will find information about the selection of
switches in chapter 2.2.

The following pages of this section will introduce the different basic PROFINET
topologies.

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Network topology

Star topology

The star topology is suitable for areas with limited geographical extension. A star-
topology is automatically created if several communication nodes are connected to
a common switch.

Star topology

Figure 3-1: Star topology

If a single PROFINET node fails or is removed, the other PROFINET nodes will
continue to operate. However, if the central switch fails, the communication to all
the connected nodes will be interrupted.

The star topology is useful in case several network nodes are
positioned close to each other, e.g. in case of installation in a
cabinet.

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Network topology

Tree topology

A tree topology is created by combining several star-shaped networks to one net-
work. Plant parts forming a functional unit are combined to star points. These are
inter-networked via neighboring switches.

Tree topology

Star topology

Star-topology network

Figure 3-2: Tree topology

One switch operates as a signal distributor in the star point. Since the switch routes
messages based on an address, only those messages will get to a neighboring
distributor which are really required at this distributor.

The tree topology is a typical example for an automation plant
being grouped into different manufacturing islands.

Page 53 / 190

Network topology

Line topology

The line is a well-known topology used in automation. It is used for applications in
extensive automation plants such as conveyor belts, but also for small machine
applications. PROFINET devices equipped with an integrated switch facilitate the
realisation of line topologies.

Line topology
PROFINET device
with integrated switch

Figure 3-3: Line topologies with internal switches

The cabling of PROFINET devices is thus possible without using additional switch-
es.

When using line topologies, bear in mind that in case of a line
interruption (e.g. outage of a device), the devices located
behind the failed device can no longer be contacted. This can
be prevented by extending the line to a ring structure.

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Network topology

3.2 Applicable transmission media
Copper cables and optical fibers are available for a wired connection of network
nodes. The cable used must meet the requirements of the planned automation
project. For this purpose, the cable manufacturers offer a range of PROFINET ca-
bles that are differentiated by their applications and special properties.

The following section describes the main item to be considered when selecting the
PROFINET copper and optical fiber cabling. Compared to copper cabling, the opti-
cal fiber cabling has additional typical parameters such as attenuation and used
wavelength which primarily restrict the length of the transmission link.

In the Annex to this document, in addition to an overview of typical cable properties
you will find a description of the transmission media as well as their application
ranges and versions.

When selecting the transmission medium you should bear in
mind an adaptation of the transmission medium to possible
influences in the application area (e.g. chemical, electrical or
mechanical).

Some examples are provided in the annex to illustrate the
determination of cabling components. Pre-assembled and
field-assembled cables are also described.

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Network topology

The correct installation of the PROFINET cabling must be
considered in the design. Make sure the allowed distance
between power cables and data cables will note be exceeded.
For more information, please see the PROFINET Installation
Guideline Order No: 8.071.

The PROFINET channel is part of the transmission line which
is defined as an end-to-end link. In addition to the channel,
the end-to-end link also includes all connectors and link inter-
sections.

The channel itself corresponds to the PROFINET end-to-end
link exclusive of the first and last connector.

3.2.1 PROFINET copper cabling
A PROFINET copper cable is 4-core, shielded copper cable (star quad). The differ-
ent types of cables vary in

• the structure of the wires (solid core / stranded for fixed / flexible applica-
tions)

• and / or the jacket material and construction.

The cores are color-coded, wire pair 1 is yellow and orange, wire pair 2 is white and
blue. The cores in each pair are arranged to be diametrically opposite within the
cable.

As in standard Ethernet applications, the maximum distance between the end
points of communication is limited to 100 m when using copper cabling. This trans-
mission link has been defined as PROFINET end-to-end link.

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Network topology

For automation plants you may only use PROFINET cables.

Application-neutral cabling (e.g. based on existing building
cables) may only be used in network areas that correspond to
conformance class A (e. g. to interconnect automation islands).

However it is recommended to use PROFINET cabling for this
application (e.g. in order to cover higher conformance class
requirements).

The common installation of power cables and copper cables for
communication is subject to regulations in order to minimize the
electromagnetic influence of power cables on the communica-
tion lines. Optical fibers however are not subject to these elec-
tromagnetic influences (see chapter 3.2.2).

Regulations for the common installation of power cables and
PROFINET copper cables must be observed for the design of
cable routing.

Follow the instructions provided in the PROFINET Installation

Page 57 / 190

Network topology

Cable types

PROFINET copper cables are categorized in different types which are mainly differ-
entiated by the relevant applications:

• Type A cables are designed for fixed installations. This cable type is not
subject to any motion after being installed.

• Type B cables are designed for flexible installations. This cable type al-
lows for occasional motion or vibrations.

• Type C cables are designed for special applications (e.g. for continuous
movement of the cable after being installed). This includes e.g. applica-
tions such as trailing chains or festoons.

Special properties of some copper cables, such as flexibility
for use in trailing chains or construction using flame retardant
materials, can reduce the maximum length of a copper cable
to less than 100 m.

Observe the manufacturer data for cables and connectors.

In addition to the special properties of PROFINET copper
cables, the Annex of this document provides detailed data
concerning the individual cable types.

Page 58 / 190

Network topology

Types of PROFINET copper cables

A number of special cable types are available for PROFINET. The most commonly
used PROFINET cable types as well as their applications are listed below:

• PE cables: PE cables are suitable for installation in areas where constant
humidity must be expected.

• Earth cables

• Flame retardant non corrosive cables (FRNC cables): Suitable for in-
stallation in areas where special fire protection regulations must be ob-
served, e.g. halls with public access.

• Trailing cable for installation on moving machine parts.

• Festoon cable

• Ship wiring cable (with approval for shipbuilding): For installation on
board ships and offshore units.

You should only use cables that have been specified as
PROFINET cables by the manufacturer. Only such cables will
ensure trouble-free operation of the network.

Observe the information material provided by the cable manu-
facturer.

You will find further information about the installation and
grounding of copper cabling in the PROFINET Installation

Page 59 / 190

Network topology

Grounding and equipotential bonding of copper cabling

When installing PROFINET copper cables correct grounding of the cabling as well
as equipotential bonding must be provided. This does not apply to optical fibers.

The cable shield must be properly grounded at both ends of every cable, i.e. at
each connected network node. In addition, equipotential bonding should be used
to prevent large ground currents flowing along the screen of the cable. The equipo-
tential bonding cable carries the earth currents which would otherwise be dis-
charged through the copper PROFINET cable shield.

Grounding of the cable shield at each end is normally achieved via the connectors
which provide a low resistance path from the cable shield to the local device earth.
However, it is also very important that the device is properly earthed.

You will find information about the assembly and the ground-
ing construction as well as about the equipotential bonding in
a PROFINET network in Annex 9.8 of this document as well
as in the PROFINET Installation Guideline Order No: 8.071.

Device manufacturers’ guidelines will generally show the
recommended way to connect the device to the local ground.
These instructions should be followed when given. Otherwise
you should always ensure a low-resistance route from the
device earth to the local earth.

Proper grounding of the cable shield together with equipotential bonding reduces
the susceptibility of the network to electrical interference.

Page 60 / 190

Network topology

The grounding of the PROFINET network and of the network
nodes can be designed as grounding system with a common
equipotential bonding and a common system grounding. For
the design of the PROFINET copper cabling you should ac-
count for a grounding as well as for an equipotential bonding
in the automation plant.

Poor earthing is a common cause of problems in PROFINET
systems. Incorrect grounding as well as being an electrical
hazard, can also cause errors in the automation system that
can damage to people and machinery.

Page 61 / 190

Network topology

3.2.2 PROFINET optical fiber cabling
In areas where electromagnetic interference may be present or significant earth
potential differences are expected it is recommended that fiber optic (FO) connec-
tion is used. Fiber optic connection can completely remove problems caused by
electromagnetic interference (EMI) and/or ground equalisation currents flowing in
copper cable screens

Cabinet

EMI
Separate
local
FO Media converter
ground

EMI

FO

Figure 3-4: Application of optical fiber technology for EMI

Figure 3-4 shows the application of optical fiber technology for the connection of
network nodes and / or switch cabinets in areas subject to electromagnetic interfer-
ence or separate local earths.

The benefits of optical fibers over copper cables are::

• FO cables can bridge larger distances than copper.

• FO cables provide total electrical isolation between plant areas.

• FO cables are totally immune to electromagnetic interference (EMI).

Below you can find a description of the different fiber types that can be used for the
design of the PROFINET network.

Page 62 / 190

Network topology

Fiber types

Four different fiber types can be employed when using optical fibers (FO) for
PROFINET. The fiber types must be selected according to requirements given by
the planned automation project (see chapter 2).

The following fiber types are available:

• Plastic optical fiber (POF)

• Glass fiber (multi-mode)

• Glass fiber (single-mode)

• Glass fiber with plastic jacket (hard-cladded silica fiber (HCF) or plastic-
cladded fiber (PCF))

The key parameters of optical fibers are listed below.

Specific attenuation of the fiber

The specific attenuation of the fiber depends on the operating wavelength and is
indicated in dB/km. The maximum values for the different fiber types, based on IEC
61784-5-3, are shown in Table 3-1.

Maximum
Fiber type Wavelength
attenuation

650 nm
POF ≤ 230 dB/km
(LED excitation)

Multi-mode ≤ 1.5 dB/km 1300 nm

Single mode ≤ 0.5 dB/km 1310 nm

HCF / PCF ≤ 10 dB/km 650 nm

Table 3-1: Specific attenuation of fiber types

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Network topology

Maximum FO transmission path

The maximum FO cable length is limited due to the attenuation of the optical signal
within the fiber, The optical wavelength that is used will also have an effect.

Transmission path
Fiber type Core diameter Sheath diameter
(typ. values)

POF 980 µm 1000 µm up to 50 m

HCF / PCF 200 µm 230 µm up to 100 m

Multi-mode 50 or 62.5 µm 125 µm up to 2,000 m

Single-mode 9 to 10 µm 125 µm up to 14,000 m

Table 3-2: Attainable transmission links of optical fiber types

The maximum transmission link is a criterion for the design of
the optical fiber link. The maximum PROFINET end-to-end
link attenuation of optical fiber links however is decisive.

Page 64 / 190

Network topology

Maximum permissible PROFINET end-to-end link attenuation

Table 3-3 summarizes the maximum admissible attenuation values, based on the
IEC 61784-5-3 and IEC 61300-3-4 standard for optical transmission links.

Maximum PROFINET end-to-
Fiber type Wavelength
end link attenuation

650 nm
POF 12.5 dB (LED excita-
tion)

62.5/125 µm : 11.3 dB
Multi-mode optical fiber 1300 nm
50/125 µm : 6.3 dB

Single-mode optical fiber 10.3 dB 1310 nm

HCF / PCF 4.75 dB 650 nm

Table 3-3: Maximum permissible PROFINET end-to-end link attenuation

When using optical fiber links, make sure that the maximum
permissible PROFINET end-to-end link attenuation are ob-
served as taken from IEC 61300-3-4.

These limit values already include attenuation reserves.

Additional junctions in optical cables

Additional junctions in the link (splices or plug connections) cause an additional
attenuation of the transmitted optical signal. Plastic optical fiber (POF) and hard-
cladded silica are often assembled in the field using simple tools. This practice has
been accounted for by means of a higher attenuation for the junction. Typical values
are shown in Table 3-4.

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Network topology

Fiber type Plastic optical fiber /
Optical fiber
Connection Hard-cladded silica / PCF

Per thermal
0.3 dB Impossible
splice connection

Per pair of connectors 0.75 dB 1.5 dB

Table 3-4: Attenuation of splices and connector pairs

Use of different fiber types

The use of different fiber types in one plant often produces costs due to additional
materials or tools being required. Although it is possible to use various types of fiber
in the same plant, this should only be done in exceptional cases.

The use of different types of fiber The use of different types of fiber
makes sense: does not make sense:

If, within one plant, numerous links can If most of the links have to be config-
be realized using plastic fiber and only ured as glass fiber and only a few links
one link, due to its length, requires the can be realized using plastic fiber. This
use of glass fiber. In this case the over- could cause higher costs due to the
all costs would be higher if all links were additional treatment of the plastic fiber
realized using glass fiber. required (tools, material).

Table 3-5: Use of different fiber types

Page 66 / 190

Network topology

Attenuation of an optical fiber link

The secure operation of an optical fiber transmission system requires that optical
signals reaching the receiver have a sufficient signal strength. The PROFINET end-
to-end link attenuation must not exceed the maximum permissible attenuation val-
ue.

The following parameters could have an influence:

• Specific attenuation of the fiber

• Additional junctions in optical cables

In order to achieve reliable communication over optical fibers the following condition
should be checked:

Transmit power - total attenuation ≥ receiver sensitivity

For the design of an optical fiber link, the specified limit values
indicate the maximum transmission link length. You should
also use a simple attenuation calculation to check the link.

You will find examples for the selection of cabling components
for optical fiber links in the Annex of this document. In addition
you will find an example for the determination of the attenua-
tion balance.

However bear in mind that this is only a verification
which by no means replacing potential acceptance
measurements.

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Network topology

3.2.3 Selection of required connectors
PROFINET cables are equipped with connectors at both ends. The combination of
connectors at the cable and at the socket is considered as a connector pair.

The connectors at both ends of the cable must also be in-
cluded. Each of them form a pair with the socket of the termi-
nal device.

Detachable connections including wall break-throughs and
transition points are also part of the connectors. You will find a
short description of them in the Annex.

Page 68 / 190

Network topology

Connectors for copper cabling

For the design of your PROFINET network you should bear in mind that the number
of detachable links within an end-to-end link is limited.

Number Maximum
Cabling example of two network components
of pairs distance

End-to-end link

100 m Channel
2 100 m

4 100 m

6 100 m

IP20 environment Connector Coupler

Table 3-6: Transmission link length and connector pairs (copper)

If the specified cables are used in combination with the speci-
fied connectors, a maximum cable length of 100 m can be
achieved when using up to six connector pairs. You should try
to use as few plug connections are possible since each plug
connection represents a potential disturbance source.

In case more than six connectors are required for an applica-
tion, you have to make sure that the attenuation values for the
entire link are observed. (channel class-D values)

Page 69 / 190

Network topology

Connectors for optical fiber links

The maximum number of detachable connections for a channel based on optical
fiber is limited, similar to a channel based on copper cabling.
Maximum distance
Number
Cabling example of two network Optical
of
components POF HCF fiber
pairs
MM / SM

End-to-end-link

Channel
2,000 m /
2 50 m 100 m
14,000 m

2,000 m /
4 42.5 m 100 m
14,000 m

2,000 m /
6 37 m 100 m
14,000 m

IP20 environment Connector Coupler

Table 3-7: Transmission link length and connector pairs (FO)

The comparably high attenuation of POF fibers, combined
with the simultaneous use of several connectors, has a large
impact on the maximum length of a POF connection. This
should be considered in case you use POF fibers in a net-
work.

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Network topology

3.3 Definition of network topology
Based on the information available to you, you should now define the topology of
your planned automation project.

Please proceed as follows:

Step 1: Precisely define the position of all network nodes in the automation
plant. Determine which network nodes must be installed together in
one location. Based on this positioning, define your topology.

Furthermore, connect the individual components, bearing in mind
to check whether the PROFINET devices are already equipped
with switches.

Step 2: This step considers PROFINET devices with special requirements
in terms of synchronisation. The high degree of time requests re-
quires a separate consideration of these devices in the topology
definition.

All PROFINET devices supporting IRT must be connected to
switches supporting IRT. All devices not supporting IRT can
still be connected conclusively to the existing network.

Bear in mind that any replacement of devices in live operation
will interrupt an existing line structure. In order to ensure the
availability, you should consider using additional switches or
extending the line to a ring structure.

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Network topology

Step 3: Next the transmission medium must be selected. Determine which
links shall be designed as optical fiber or as copper connection.

Check whether the network node supports this transmission me-
dium. If necessary, you should install additional media converters
in the transmission link (see chapter 3.4).

Make sure here that the cabling is compatible with the envi-
ronmental conditions.

Also make sure not to exceed the maximum permissible
number of connectors within a link.

In the Annex, you will find a description of the connectors currently available for
PROFINET. The following pages provide some example plants and their topology.
These examples can only show a brief overview of possible PROFINET topologies.

Page 72 / 190

Network topology

Example 1: Factory automation

The topology for an automation plant, designed for factory automation, could have
following structure.

Switch cabinet I Control room Switch cabinet II

Plant area A Plant area B

Figure 3-5: Example of a factory automation

In this example, the controllers and switches are installed in separate switch cabi-
nets next to the production line. All controllers are able to communicate with each
other without limitation. Due to the large distance between the plant areas, the links
between the switches are realized by means of optical fiber.

In plant area A, the IO devices are located near the manufacturing process and
connected via a line structure while plant area B, in addition to a synchronous con-
nection of drives, foresees additional PROFINET devices with cyclic communication
such as IO devices and IO panels.

This example clearly shows the combination of different to-
pologies.

Page 73 / 190

Network topology

Example 2: Automation of a machine

The following example shows the automation of a machine. Here, the plant is sub-
divided into several areas which assume different functions. The response times of
the plant typically are very short.

Switch
Control
cabinet
room

Machine area

Figure 3-6: Example of a machine automation

While the operator panel is installed in the control room and the IO controllers out-
side the machine area are in a switch cabinet, the IO devices and an IO panel are
located in the machine area.

The PROFINET devices which do not require a synchronous connection are posi-
tioned first and connected to the switch. The special requirement in terms of deter-
minism (position-controlled axes) also implies the drives to be synchronously con-
nected to a switch supporting IRT. Non-IRT PROFINET devices can also be routed
via the IRT switches jointly with the IRT traffic.

Page 74 / 190

Network topology

Example 3: Process automation

Process automation amongst others covers chemical industry applications. Here,
the network structure is e.g. used to link

• chemical reactors

• power plants

• or chemical plants.

The requirements in terms of response times are typically lower in process automa-
tion than they are in manufacturing or machine automation.

Control room
Switch cabinet I
Switch cabinet II

Plant part A Plant part B

Figure 3-7: Example plant process automation

The control room monitors both processes which are divided into plant part A and
B. Both plant parts have a local switch cabinet which is equipped with a switch and
an IO controller.

Due to the vast extent of the plant, the network nodes are linked via a line structure.
This reduces the amount of cabling required.

Page 75 / 190

PROFINET Design Guideline Summary

PROFINET Design Guideline Summary

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